Why Fitted Sizing Runs the Way It Does
A fitted cap is sized in eighths of an inch and has no adjustment at all. That looks like an inconvenience next to a snapback that fits everyone, and it is - but it is the direct cost of the thing people buy fitteds for.
The closure is what a snapback trades for its adjustability: a plastic strip across the back of the crown. Remove it and the cap's line runs unbroken, which is the entire aesthetic argument. You cannot have both.
Why eighths
The increments are small because the tolerance is small. With no closure, the cap either sits correctly or it does not, and a quarter-inch is the difference between those two states. Adjustable caps can afford coarse sizing because the strap absorbs the error.
Why two people the same size can prefer different caps
Head circumference is one number describing a three-dimensional shape. Crown depth, how far down the cap sits, and head shape both affect how a fitted wears, and neither is captured by the measurement.
This is why trying one on beats measuring where it is possible, and it is a genuine argument for the independent stockists over ordering blind. Find one near you →
Why they do not stretch much
A structured fitted holds its shape by design. Some give develops in the sweatband over time, but the crown is built not to relax, which is the same property that keeps the cap looking right after a year.
Do not buy tight expecting it to give.
What to do about it
Measure properly, and go up when between. How to measure → · Fitted caps →
FAQ
Why are fitted caps sized in eighths?
Because there is no closure to absorb error. With an adjustable cap the strap covers a range; with a fitted, a quarter-inch is the difference between fitting and not.
Do fitted caps stretch out?
Not much. The sweatband gives slightly over time, but a structured crown is built not to relax. Do not buy tight expecting it to give.
Why does my size feel different in different caps?
Circumference is one number describing a three-dimensional shape. Crown depth and head shape both affect fit and neither shows up in the measurement.